| In the early limb bud, Dlx5 and Dlx6, members of the Dlx homeobox gene family, are expressed in condensed mesenchymal cells that differentiate into chondrocytes. Analyses of Dlx5 and compound Dlx5/6 mutant mice reveal that Dlx5 and Dlx6 positively regulate chondrocyte differentiation in a functionally redundant manner. We misexpressed Dlx5 and Dlx6 in chicken embryo limb bud mesenchymal cells both in vitro and in vivo to map the functional domains of their chondrogenic stimulatory function. The amino-terminal domain of Dlx5 was required for its chondrogenic stimulatory function. In contrast to Dlx5, both the amino- and carboxy-terminal domains of Dlx6 were required for this conserved function. Results of the functional domain mapping of Dlx5 in vivo were consistent with the in vitro data, and misexpression of Dlx5 or Dlx6 in vivo resulted in reduced ossification of all skeletal elements in the wing. |
